74 THE NAUTILUS. 



lies every^vllere our best chance of ascertaining the principles of 

 evolution. 



The varieties of Helix nemoralis are classified according to the 

 following principles : First, variation in the ground-color of the 

 shell, with the name Uhellula for yellow shells, rubella for pink shells, 

 petiveria for pale brown or fawn-colored shells, etc. Secondly, 

 variation in the banding, for which a band-formula is used. The 

 typical shell has five bands, three above the periphery and two 

 below, and its formula is accordingly 12345. If a band is missing, 

 a is placed in its stead — thus 12045 has the third band of the type 

 missing, while 00000 is the formula for a bandless shell. If two 

 or more bands are coalesced, they are bracketed together, thus, 

 12(345). If a band is imperfectly developed, it is indicated as a 

 small figure below the line, thus, 12345. If a band is split into two, 

 the number is repeated, as 1233(45), while an extra band which 

 cannot be assigned to any of the usual five, is represented by an X, 

 as 003X00. The formula should always be taken from near the 

 mouth of the shell. These, then, are the ordinary kinds of varia- 

 tion, while other unusual characters are expressed in suitable terms, 

 as tenuis for a very thin variety, compressa for a depressed form, 

 viinor for a small form, albolabiata for a white-lipped shell, etc. These 

 terms are used in conjunction Avith one another, to indicate the differ- 

 ent peculiarities of any given shell. The band-formulae express them- 

 selves, and need not, as a rule, have the name of their author quoted 

 after them. But in introducing these band-varieties to the American 

 fauna, I have given the names of their first recorders, as a hint to their 

 history in Europe. For certain of them, I have given special names 

 bestowed by French authors — as brissonia for petiveria 12345. If 

 these names are to be adopted, it will be necessary to bestow many 

 new ones, as a large number of combinations have not come under 

 the notice of the aforesaid authors, but to my mind it is more con- 

 venient to use the baud-formulre in conjunction with the color- 

 names. There is only one thing to be said for the names given to 

 combinations, that if misprinted they can hardly lead to any real 

 confusion, whereas band-fornudie may be misprinted easily enough 

 in such a way as to lead to erroneous records, Avhich may never be 

 corrected. 



All the shells of H. nemoralis I have seen from the colony at 

 Lexington, Va., were collected by Prof. J. H. Morrison, and number 

 altogether 103. The first consignment, sent me through Mr. H. A. 



